1. Field of the Invention
The present invention relates to agricultural irrigation systems. More particularly, the invention relates to an improved track assembly for an irrigation system.
2. Background
Agricultural irrigation systems such as central pivot irrigation machines and lateral move irrigation machines are commonly used to irrigate crops. A central pivot irrigation machine typically includes, among other things, a central pivot communicating with a pressurized water supply and a series of spans formed from mobile support towers connected to the central pivot and to one another by truss-type framework sections. A water distribution conduit is supported by the framework sections and a number of sprinkler heads, spray guns, drop nozzles, or other fluid-emitting devices are spaced along the length of the conduit. A lateral move irrigation system is similar except it does not include a central pivot but instead has several aligned spans that move laterally across a rectangular-shaped field.
The mobile towers of central pivot and lateral move irrigation systems are typically supported on wheel and tire assemblies that are driven by suitable motors. These wheel and tire assemblies sometimes slip, get stuck, and/or create ruts, especially in wet low-lying areas or on hills.
To alleviate these problems, a mobile tower's tires can be replaced with track assemblies similar to those installed on earth-movers and tractors. Track assemblies provide better traction and have a much larger footprint and better ground “floatation” and therefore don't create ruts and damage crops as much as tires do.
Unfortunately, known irrigation system track assemblies are complex and expensive and are therefore not practical for many applications. Moreover, known track assemblies sometimes provide too much traction and are therefore difficult to guide in a circular or other non-straight path without creating excessive stress on the irrigation system. In fact, applicant has discovered that known track assemblies can cause the spans of smaller irrigation systems to buckle while turning. Similarly, applicant has discovered that known track assemblies create excess off-set loading on gearbox output shafts and other irrigation system components.
To allow an irrigation system to more easily follow a circular or other non-linear path, its wheels or track assemblies can be provided with a selected steering angle or tow. Unfortunately it is difficult and time-consuming to set the tow on existing irrigation system track assemblies.